Communication system, key managing/distributing server, terminal apparatus, and data communication method used therefor, and program

Abstract

To provide a mobile communication system that can prevent unauthorized use of an encryption key otherwise caused by loss thereof and that can securely perform a direct communication between terminals using the encryption key. A portable terminal apparatus 1-1 transmits a P2P communication trigger to a portable terminal apparatus 1-n through a key managing / distributing server 3. In response to the transmission / reception of the trigger, the portable terminal apparatuses 1-1 and 1-n establish IPsec data sessions with the key managing / distributing server 3 through a SIP server 2 and a secret key is distributed per communication to the portable terminal apparatuses 1-1 and 1-n from the key managing / distributing server 3. The portable terminal apparatuses 1-1 and 1-n establish an IPsec data session therebetween using the secret key, thereby performing a P2P communication. The key managing / distributing server 3 performs key delivery control for switching to the session and establishing the session, with respect to the portable terminal apparatuses 1-1 and 1-n.

Description

TECHNICAL FIELD[0001]This invention relates to a communication system, a key managing / distributing server, a terminal apparatus, a data communication method used therefor, and a program thereof and, in particular, relates to a method of performing a data communication by securely obtaining a dynamically generated encryption key.BACKGROUND ART[0002]In recent years, for portable terminal apparatuses such as portable telephones, following the increasing multifunctionality thereof, a method has been proposed that directly connects between portable terminal apparatuses by short-range wireless communication or the like to perform a data communication therebetween, in addition to wireless communication through a wireless base station. Such a conventional technique is described, for example, in Unexamined Patent Publication No. 2003-087267.[0003]In that event, in the case of connecting the portable terminals by P2P (Peer to Peer: direct communication between terminals) communication (includ...

AI Technical Summary

Benefits of technology

[0029]In the communication system of this invention, in response to a communication request as a trigger, the key managing / distributing server distributes a unique secret key to both terminal apparatuses, which will be in communication, per communication between the terminals. Accordingly, since a different secret key (encryption key) is used for each communication, security of secret keys becomes high. Further, although a different secret key is used each time, it is not necessary to store those secret keys on the terminal apparatus side. Consequently, the communication system of this invention enables a secure P2P (Peer to Peer: direct communication between terminals) data communication between terminal apparatuses, particularly between portable telephone terminals.

[0039]With the structure and operation as will be described hereinbelow, this invention achieves effects that can prevent unauthorized use of an encryption key otherwise caused by loss thereof and that can securely perform a direct communication between terminals using the encryption key.

Problems solved by technology

Note, however, that the P2P communication by the short-range wireless communication cannot be realized when the terminal apparatuses are remote from each other.

In the foregoing conventional data communication method, there is a problem that publishing one's own secret key results in that the secret key is possessed by a plurality of persons and, therefore, there is a possibility of unauthorized use thereof.

Further, when the public key cryptosystem is used, complicated encryption and decryption processes are required, which is thus not suitable for processing in a small-scale terminal such as a portable terminal apparatus.

Further, having a plurality of secret keys for respective communication partners extensively uses a storage area of a memory of a portable terminal apparatus storing those secret keys and, if any of the communication partners loses one's own portable terminal apparatus, the plurality of secret keys stored in its memory leak out, which raises a big problem.

However, this method lacks the real-time performance and, further, the same key should be delivered also to a communication partner with a trigger when a sender wishes to start a communication.

According to the nature of HTTP (HTTPS), however, it is difficult to trigger key delivery from a key managing / delivering server side to a terminal apparatus (HTTP client).

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